Conventional braiding machines may be comprised of a plurality of tow carrier devices dispersed around a braiding machine track. Braided products formed by conventional braiding machines may be comprised of a two over, two under (2×2) braid architecture in which two clockwise traveling tow carrier devices may pass over two counterclockwise traveling tow carrier devices and under two counterclockwise traveling tow carrier devices in a repeating pattern. Tow carrier devices may travel circumferentially as well as radially inwards and outwards around the braiding machine track to promote the intertwining of tows to form the braided structure.
Braided products comprised of 2×2 braid architectures may be overbraided onto preforms of complex geometry in which the largest cross-sectional portion of the preform may be larger than that of the smallest cross-sectional portion of the preform. One example of a preform of complex geometry may be a classic Coca-Cola® bottle; wherein a straw is symmetrically affixed in the center of the opening. The straw may be analogized to the center of a braiding machine and the exterior surface of the bottle may be analogized to a preform having a complex geometry onto which braid may be formed. The formation of the braided structure may be initiated at the top of the coke bottle. The braiding machine track may be located near the base of the bottle, or the largest cross-sectional portion of the coke bottle. Tows affixed to tow carrier devices traveling around the braiding machine track intertwine to form a braided structure around the outer surface of the coke bottle which may be analogous to a sleeve covering the surface of the coke bottle. The coke bottle may be vertically advanced as the braiding structure forms on the outer surface of the coke bottle. The cross section of the coke bottle transverse to the longitudinal axis represented by the straw may be transitory and represented as a series of circular shapes having a series of varying diameters. The diameter of the opening of the coke bottle may comprise the smallest cross-sectional diameter, while the base may comprise the largest cross-sectional diameter. In one example, the ratio of cross-sectional diameter of the largest portion of a preform of complex geometry to the smallest portion of the preform of complex geometry may be 5 to 1, 3 to 1, 10 to 1 and other variations, such as 5 to 2 and 3 to 2 etc. In additional examples, if the largest cross-sectional portion of the preform were to exceed three times that of the smallest cross-sectional portion of the preform, bunching or wrinkling of the braided product may occur. A higher ratio of the largest to the smallest cross-sectional diameter of the preform may exacerbate these structural imperfections.
Conventional 2×2 braided products may experience low compaction of tows within the braided structure as well as high compaction of tows within the braided structure as a result of the complex geometry of the preform on which the braided product may be overbraided. A low compaction area may be described as an area in which the tows within the braided structure may be spaced apart while a high compaction area may be described as an area in which tows may be touching, overlapping or stacked on top of another. In a case in which the largest portion of the preform may exceed three times that of the smallest portion of the preform, bunching or wrinkling of the braided product may occur. Bunching or wrinkling may occur when tows within the braided structure may not be compacted, in a high compaction situation, any closer together. This may place stress on the braided structure and may cause the braided structure to bunch or wrinkle to allow further compaction of the braided structure to take place. This distortion of the braided structure is undesirable.
The creation of braided structures with reduced distortion when overbraided onto preforms of complex geometry, in which the ratio of the largest cross-sectional diameter of the braided product to the smallest cross-sectional diameter of the braided product may exceed a generally three to one ratio, is desired.
Braided structures created using traditional maypole style braiding machines may conventionally be produced in a tubular form. Braided tubular sleeves may be overbraided onto preforms with complex cross-sectional geometries, and may conform to the shape of these preforms. However, this may lead to disruption in the braided structure; inducing areas of high and low tension and resulting in variation of bias angle across the preform. This may be especially evident when preforms of varying large and small cross-sectional geometries along the longitudinal axis may be overbraided with braided sleeve products. In these products, areas of large cross-sectional geometries may experience high tension and distorted braid geometry, or high bias angles, while small cross-sectional geometries may experience very low tension, low bias angles and may not conform well to smaller cross-sectional geometries especially in cases in which the difference between the large and small cross-sectional geometries may be significant, including 5:1, 8:1 or 10:1 ratios.
A method for the creation of a braided product which may maintain the same tension over all sections of a preform with varying cross-sectional geometry is desired.
Further, tubular braided products overbraided onto preforms such as flexible tubing may tend to bunch or kink at bending locations. In a continuing discussion of a Coca-Cola® bottle as a preform of complex geometry, two coke bottles may be affixed such that each top of each coke bottle is coincident and concentric. The location at which the two coke bottles are affixed to one another may be defined as the bending location. At this location, the smallest diameter cross-sectional portions of the coke bottles are in contact and when affixed may comprise a continuous section of small cross-sectional diameter. Within commercial braided products, it is desired to orient the two affixed coke bottles parallel to one another. To achieve this, the two affixed coke bottle tops must be curved in relation to the axis of each bottle defined by the straw. As a result, it may be envisioned that as the affixed coke bottle tops are curved, one portion of each top must become stretched, while another portion must compress to form a “U” shape such that the two coke bottles may become parallel to one another. The distortions resulting from such an arrangement is undesirable in commercial braided as an area of high material density, wrinkling and distortion in the braided product may be created below the bending point, or the smallest portion of the “U” shape or bending radius while an area of high tension and high bias angle may be created within the braided product over the bending point, or the largest portion of the “U” shape or bend radius. It is desired to eliminate these distortions at bending locations in braided products.
In addition, the braid architecture as well as the number of tow carrier devices present in conventional braiding machines may not be easily or efficiently altered during the braiding process. Additional flexibility in the number of tow carrier devices a braiding machine may comprise at a single point in time is desirable to maximize the diversity of products which may be produced on a single braiding machine.